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Residential Broadband: Technologies for High-Speed Access To Homes

Residential Broadband: Technologies for High-Speed Access To Homes. Raj Jain The Ohio State University Columbus, OH 43210 Jain@cse.ohio-State.Edu http://www.cse.ohio-state.edu/~jain/cis788-97/ Email questions to mbone@netlab.ohio-state.edu. 56 kbps Modems, ISDN ADSL, VDSL HFC, FTTC, FTTH

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Residential Broadband: Technologies for High-Speed Access To Homes

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  1. Residential Broadband: Technologies for High-Speed Access To Homes Raj Jain The Ohio State UniversityColumbus, OH 43210Jain@cse.ohio-State.Edu http://www.cse.ohio-state.edu/~jain/cis788-97/Email questions to mbone@netlab.ohio-state.edu

  2. 56 kbps Modems, ISDN • ADSL, VDSL • HFC, FTTC, FTTH • Cable Modems • IEEE 802.14 standard Overview

  3. Potential Applications • Video on demand (VOD) • Near video on demand (NVOD) - staggered starts • Distance learning, Teleconferencing, Home shopping • Telecommuting • Meter reading • Security Existing cable TV has the media but no switching Existing phone service has switching but not enough bandwidth

  4. Modem Modem Phone Co 56 kbps Modems • ISP’s have direct digital link (T1 or T3) • Only one D/A/D conversion  Higher speed possible • Past: • Current: InternetServiceProvider Modem Phone Co

  5. CentralOffice ADSLVDSL Twisted pair 100-500 homes Opto-Electric Fiber Coax HFC Headend Optical FTTC 10-50 homes Optical FTTH Residential Access Networks (RANs)

  6. PhoneNetwork Modem Modem Filter Filter Why Modems are Low Speed? • Telephone line bandwidth = 3.3 kHz • V.34 Modem = 28.8 kbps  10 bits/Hz • Better coding techniques. DSP techniques. • Cat 3 UTP can carry higher bandwidth • Phone companies put 3.3 kHz filters at central office  Allows FDM

  7. DSL • Digital Subscriber Line = ISDN • 64×2 + 16 + overhead = 160 kbps up to 18,000 ft • DSL requires two modems (both ends of line) • Symmetric rates  transmission and reception on same wire  Echo cancellation • Use 0 to 80 kHz  Can't use POTS simultaneously PhoneNetwork DSL DSL DSL DSL

  8. DSL Technologies • DSL: Digital Subscriber Line (ISDN) • HDSL: High data rate DSL (T1/E1 on 2 pairs) • SDSL: Single line DSL (T1/E1+POTS on 1 pair) • ADSL: Asymmetric DSL • RADSL: Rate-adaptive ADSL • VDSL: Very high data rate DSL • VADSL: Very high data rate Asymmetric DSL = VDSL • BDSL: Another name for VDSL • VDSLe: European version of VDSL

  9. HDSL • Initially T1/E1 over copper used AMI coding  Repeaters every 3000 - 6000 ft • Uses 1.5 MHz for 1.5 Mbps  Wasteful of bandwidth  Interference  Can't put more than 1 circuit in a 50 pair cable • HDSL transmits T1/E1 over two pairs using 80 to 240 kHz  repeaters at 12,000 ft • Used in PBX interconnection, cellular antenna stations, interexchange POPs • SDSL = Single pair version of HDSL. Allows POTS and T1/E1 simultaneously. Up to 10000 ft.

  10. ADSL • Asymmetric Digital Subscriber Line • Asymmetric  upstream << Downstream • Symmetric  Significant decrease in rate • 6 Mbps downstream, 640 kbps upstream • Using existing twisted pair lines • No interference with phone service (0-3 kHz) Your phone isn't busy while netsurfing • Up to 7500 m • ANSI T1.413 Standard • Quickest alternative for Telcos

  11. Why Asymmetric? • Unshielded twisted pair  Crosstalk • Downstream signals are all same amplitude  Not affected • Upstream signals start at different distances  Different amplitudes  Weak signals are highly affected • Solutions: 1. Use asymmetric rates 2. Use lower frequencies for upstream(Cross talk increases with frequencies)

  12. ADSL Status • ADSL modems have been tested successfully by over 30 phone companies • InterAccess Inc (Internet service provider) offers 1.5 Mbps/64 kbps ADSL in downtown Chicago. $200 per PC or $1000 per LAN. • Microsoft + Westell to support ADSL in Windows NT server  MS Public Network Platform • Microsoft + General Instrument, Zenith, and Motorola to support cable modems

  13. VDSL • Very High-Speed Digital Subscriber Lines • Also called VADSL, BDSL, VHDSL • ANSI T1E1.4 standardized the name VDSL and ETSI also adopted it • VDSLe to denote European version • For use in FTTC systems • Downstream Rates: 51.84 -55.2 Mbps (300 m), 25.92-27.6 Mbps (1000 m), 12.96 - 13.8 Mbps (1500 m)

  14. VDSL (Cont) • Upstream Rates: 1.6-2.3 Mbps, 19.2 Mbps, Same as downstream • Admits passive network termination  Can connect multiple VDSL modems like extension phones (ADSL requires active termination) • Unlike ADSL, VDSL uses ATM to avoid packet handling and channelization • Orkit Communications (Israel) demoed VDSL modems at Supercomm'96

  15. Hybrid Fiber Coax (HFC) • Reuse existing cable TV coax • Replace trunks to neighborhoods by fibers • 45 Mbps downstream, 1.5 Mbps upstream • MAC protocol required to share upstream bandwidth • 500 to 1200 homes per HFC link • Sharing  Security issues • IEEE 802.14 is standardizing MAC and PHY Headend Fiber Coax

  16. Cable Modems • Modulate RF frequencies into cable.Signal received at the headend and converted to optical • Cost $395 to $995 • If cable is still one-way, upstream path through POTS • $30 to $40 per month flat service charge • Successful trials in Canada using 500 kbps modems • After the trial 75% users kept the service and paid • TCI formed @Home http://www.home.net • Servers at headend to avoid Internet bottleneck • Plans to create high-speed cable backbone across US

  17. Fiber to the Curb (FTTC) Coax or TP HeadendDigital Terminal • Coax and twisted pair for the last 100-300 m • Coax is used for analog video, TP is used for POTS • Baseband  No frequency multiplexing • Passive optical network  signal is optically broadcast to several curbs  Time division multiplexing • Up to 50 Mbps downstream, Up to 20 Mbps upstream • Co-exist with POTS or ISDN on the same cable pair • Twisted pair  EMI  withstand legal 400W radio transmissions at 10 m Fiber

  18. Fiber to the Home (FTTH) • Fully optical  No EMI • Initially passive optical network  Time division multiplexing • Upstream shared using a MAC • 155 Mbps bi-directional • Need new fiber installation

  19. Tech- Typical Typical Max Homes nology Downstream Upstream Distance Per Opt. Rate Rate Unit HFC 45 Mbps 1.5 Mbps N/A 500 Shared Shared FTTC 25-50 Mbps 25-50 100 m 10-50 Mbps FTTH 155 Mbps 155 Mbps N/A 10-200 ADSL 6 Mbps 640 kbps 4,000 m 1,000 VDSL 13-50 Mbps 1.6-5 2,000 m 100 Mbps Comparison of RANs

  20. ADSL Cable Modems Phone company Cable company Switching experience No switching but high but low bandwidth ckts bandwidth infrastructure Þ Þ Point-to-point Data Broadcast. Sharing privacy More cost effective Currently 1.5 to 8 Mbps 10 to 30 Mbps Perf = fn(location) Independent of location Phone everywhere Cable only in suburbs (not in office parks) Þ New Revenue Existing customers ISDN and T1 obsolete ADSL Vs Cable Modems

  21. CableTV Headend Super trunk=Fiber Trunk=Coax IEEE 802.14 • CATV Protocol working group • Started November 1994 • Defining PHY and MAC for 2-way HFC • Downstream PHY: 1-to-n broadcast • Upstream PHY: n-to-1 • Up to 200 microsecond one-way

  22. 802.2 802.1 802.2 AAL 802.1 ATM ATM 802.14Access 802.14Access PHY PHY ATM Friendly All ATM IEEE 802.14 Protocol Stack

  23. 802.14 MAC Issues • ATM-based mandatory • Addresses: Permanent (48-bit) and14-bit local id • Slot allocation granularity: 6 bytes downstream, Upstream: Minislot = 8 bytes data + Phy + Guard • Contention method: Ternary tree

  24. IEEE 802.14 PHY • 500 homes as a reference design point • Support sub-split (5-65 MHz upstream), mid-split (5-108 MHz upstream), and high-split (5-174 MHz upstream) • Quadrature Amplitude Modulation (QAM) 64 and 256 for downstream. 6 bits/Hz  30 Mbps on 6 MHz 27 Mbps w FEC • Quadrature Phase Shift Keying (QPSK) and 16-QAM for upstream to sustain high noise  1.5 to 3 Mbps on 2 MHz • Several upstream channels per downstream channel

  25. QAM • Quadrature Amplitude Modulation, 16-QAM, 64-QAM • Two waves 90o apart are amplitude modulated using n/2 bits each to produce 2n-QAM • Used in V.34 modems. Q Axis I Axis

  26. Satellites for Data • DirecPC from Hughes • One-way high-speed connection 400 kbps SatelliteNetworkOperationCenter InternetServiceProvider 28.8kbps

  27. Wireless Local Loop • Fixed, high, directional antennas Þ Lower loss, no handoff CentralOffice BaseStation Landline

  28. Summary • High Speed Access to Home: ADSL, VDSL, HFC, FTTC, FTTH • 6 to 155 Mbps downstream, 1.5 Mbps upstream • Both cable and telecommunication companies are trying to get there with minimal modification to their infrastructure

  29. RBB: Key References • For a detailed list of references, see http://www.cse.ohio-state.edu/~jain/refs/rbb_refs.htm • IEEE 802.14 Media Access Control, Draft 2 R1, June 20, 1997 • IEEE 802.14 Physical Layer Specification for HFC networks, Draft, May 16, 1997. • ANSI T1.413, ADSL Metallic Interface

  30. References (Cont) • IEEE 802.14 Working group, http://www.walkingdog.com • The ADSL Forum, http://www.sbexpos.com/sbexpos/associations/adsl/home.html • Cable Labs, http://www.cablemodem.com • IETF IP over Cable Data Network working group, http://www.ietf.org/html.charters/ipcdn-charter.html • Cable Modem FAQ, http://www.cox.com/modemfaq.html

  31. Current Schedule 7/17/97 Priority and Multicasting on LANs 7/22/97 No Class 7/24/97 Virtual LANs 7/29/97 Gigabit Ethernet 7/31/97 Quiz 2 (No MBone transmission) 8/5/97 Residential broadband: Cable Modems, xDSL 8/7/97 Multicasting over IP and ATM 8/12/97 Multimedia over IP: RSVP, RTP 8/14/97 Wireless LANs and WANs 8/19/97 Quiz 3 (No MBone transmission)

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